This invention relates to transition metal catalysts and method for their production and use in the polymerization of olefins.
In the production of polyolefins, such as for example polyethylene, polypropylene, ethylene-butene copolymers, polymethylpentene, etc., an important aspect of the various processes and catalysts used to produce such polymers is the productivity. By productivity is means the amount or yield of solid polymer that is obtained by employing a given quantity of catalyst. If the productivity is high enough, then the amount of catalyst residues contained in the polymer is low enough that the presence of the catalyst residues does not significantly affect the properties of the polymer and the polymer does not require additional processing to remove the catalyst residues. As those skilled in the art are aware, removal of catalyst residues from a polymer is an expensive process and it is very desirable to employ a catalyst which provides sufficient productivity so that the catalyst residue removal is not necessary. High productivities are also desirable in order to minimize catalyst costs.
It is known in the art to use electron donors such as esters in the preparation of catalysts to produce stereoregular polymers. However, it would be desirable to develop new and improved catalysts and polymerization processes which provide stereoregular polymers and higher catalyst productivities.